It is often desirable to convert solid or gas carbon-containing products into hydrocarbon liquids using Fischer-Tropsch reactions. For example, the carbon based product might be coal, biomass or natural gas. These starting products are converted in a syngas generator to a synthetic gas, hereinafter referred to as “syngas”, which contains carbon monoxide (CO) and hydrogen (H2) gases. The syngas is then converted in a Fischer-Tropsch reactor, typically in the presence of an iron or cobalt based catalyst and under suitable temperature and pressure conditions, into hydrocarbon products and other effluents. These hydrocarbon products are usually widely distributed in carbon chain length (C1-C100+). At temperatures of approximately 22° C. and at atmospheric pressure, these produced hydrocarbon products include significant quantities of gas (C1-C4), liquid (C5-C20) and waxy (C20+) products. These designations of chain length for gas, liquid and waxy (solids) products are, of course, also dependent upon the relative branching of the hydrocarbon chains of the products and other known factors.
Conventional F-T synthesis of hydrocarbon products has several shortcomings. First, the synthesis is not particularly selective and can generate the wide range of hydrocarbon products having carbon chain lengths of C1 to C100+. Light hydrocarbons of very short chain lengths often need recycling and further processing in the F-T reactor to produce more desirable medium chain length hydrocarbons. Alternatively, these light gases can be burned as fuel to produce heat. Hydrocarbons having chain lengths in the upper end of this chain range, in general from C21 to C100+, are considered to be waxy rather than liquid at the above described temperature of 22° C. and 1 atmosphere of pressure. Often hydrocracking is required to break these long chain length hydrocarbons down into shorter, less viscous and more desirable liquid hydrocarbon products. However, in some locations, such as on offshore oil and gas producing platforms, it is undesirable to locate hydrocracking facilities due to weight, space and economic limitations. Thus using conventional F-T conversion processes on an offshore platform is less than desirable. Also, in remote land locations, it may be undesirable to include a hydrocracking unit as the addition of this unit raises the capital and operating expenses associated with F-T production of hydrocarbon products.
Another shortcoming in conventional F-T conversions is that significant amounts of methane are produced. A further shortcoming is that a rather limited amount of carbon monoxide within the syngas is converted in each pass through a F-T reactor. The present invention addresses these shortcomings in traditional F-T syntheses which typically include production of substantial amounts of methane and other short chain gaseous hydrocarbon products along with substantial amounts of long chain, waxy hydrocarbon products while converting carbon monoxide in a syngas to hydrocarbon products at a relatively low conversion rate.